Under time-of-use rates, higher prices are charged for electricity used during those parts of the day when demand and system costs are higher, with lower charges when demand and system costs are lower. In the Ohio project, 160 customers of the Dayton Power and Light Co. (100 on a seasonal time-of-use electricity rate and 60 on the control rate) became part of an 18-month study from 6/76 through 11/77. The experimental rate schedule used two rating periods during weekdays and a single rating on weekends and holidays. Electricity-consumption patterns of customers on the TOU rate and a control group on the existing (declining block) rate showed that customers on the TOU rate used less electricity than the control group during the six-hour period of peak prices and used correspondingly more electricity during the base period of low prices. As a result of these offsetting effects, overall consumption was unaffected. Tests of hypotheses showed the peak-period decreases (ranging from 21 to 38% on a monthly basis) to be statistically significant. On the other hand, the base-period increases were not significant (at the 5% level) because of much larger customer-to-customer variation in base period usage. Other significant findings were that the diversified demand of the residential class at the time of system peak was, in the two months examined (August and September 1976), significantly lower for the experimental group. The residential class load factor based on that diversified demand was significantly higher for the experimental group during August. At the time of system peak, diversified demand was lower by 29 to 40% and the associated load factor was 135 to 161% of that under the control rate.